Tapping on TNT with any sword enchanted with fire aspect makes the TNT activate.
Steps to Reproduce:
-enchant any sword with fire aspect
-place one TNT on the ground
-tap the TNT using the fire aspect sword (or right click in Windows 10)
-the TNT will ignite (in PE)
I've checked the wiki just in case it was an exclusive feature but nothing there says that it can be activated using a sword.
I discovered this in my survival world while decorating using TNT (great idea) and accidentally tapped it with my fire aspect sword. Then I tested it in a creative world and had the same results.